CODEWITHSUNDEEP
pythonpython-2.7
Esteban G. Gutierrez
Esteban G. Gutierrez

Reputation: 195

What is the interpreter really seeing and executing for bitwise operators?

I am trying to understand bitwise operators in Python 2.7 (<<, >>, &, |, ~ and ^), so my question is: what is the interpreter really seeing and executing? When:

>>> 3 >> 0
3
>>> 3 >> 1
1

and why

>>> 3 >> 2
0

and after that if you increment the second number by one the answer will continue to be 0.

They treat it as if it were a string of bits, written in twos-complement binary. But I do not understand what happens here.

Upvotes: 0

Views: 52

Answers (1)

pascalhein
pascalhein

Reputation: 5866

Have a look at the binary representation of these numbers and imagine that there are infinite zeroes to the left:

...0000011 = 3

Now, what >> does is it shifts the binary representation to the right. This is the same as deleting the last digits:

If you shift by 0 places, nothing changes. Therefore, 3 >> 0 is 3.

If you shift by 1 place, you delete the last binary digit:

...0000011 >> 1 = ...000001 = 1

Therefore, 3 >> 1 is 1.

If you shift by 2 or more places, all of the binary ones will be deleted and you are left with only zeroes:

...0000011 >> 2 = ...00000 = 0

This is why 3 >> 2 (or more than 2) is always 0.

Upvotes: 5

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